This invention relates to a shuttleless loom of the type having unidirectional weft thread carriers.
It is known that, in addition to conventional weaving looms wherein the weft thread is inserted between the warp threads by means of a shuttle, reciprocating to and fro and housing a spool or cop with the thread thereon, so called shuttleless looms have been developed, wherein the weft thread is inserted by a weft thread carrier which is spool-less and configurated such as to grip the weft thread at one side or end of the shed and release it at the opposite side or end after having crossed the whole width of the fabric. Specifically, a number of such carriers are provided, each carrier being first brought to a position for gripping the weft thread supplied by a spool arranged on a stationary support, and then thrown across the shed by means of a torsion bar which confers to the stationary carrier the necessary acceleration and velocity, as required by the weight and thickness of the weft and by the cloth width, whereafter the thread is cut off, the carrier brought to stop and then returned to its initial position, e.g. by means of a conveyor located under the warp. The carriers operate one after the other. Looms operating on this general principle are commonly referred to as Sulzer shuttleless looms.
The advantages provided by such looms over the looms of conventional design are noteworthy. Indeed, since it is no longer necessary to transfer the thread-carrying spool across the shed, it becomes possible to effect a marked reduction in the size of the movable carriers and, accordingly, in the moving masses involved, with resulting lower energy requirements and increased throwing velocities. This velocity increase brings about a remarkable increase in the production rate with respect to the traditional looms, for a given machine size.
By contrast to such advantages over the traditional looms, the shortcomings of the system just described should be taken into account. Firstly, it should be noted that the stopping of the carrier on completion of the weft insertion step causes a waste of useful energy, which becomes higher as the throwing velocity increases, that same energy amount having to be replenished on the next throw. Furthermore, the noise and vibration should not be underestimated which are constantly set up by the sudden stop of the carriers on completion of the weft insertion step. There exists also a limitation to the reciprocation speed of the sley which, when using high carrier throwing velocities, is bound to reciprocate so quickly that remarkable and unacceptable vibrations are generated as a certain throwing velocity is exceeded. The carriers themselves, owing to the mechanical stresses whereto they are constantly subjected along their tails and tips, have to be made of a suitable material. All this prevents the production rate of such known looms from exceeding a given output limit.